1. Field of the Invention
The present invention relates to a thin film transistor, a manufacturing method thereof, and a display device.
2. Description of the Related Art
As one type of field-effect transistor, a thin film transistor whose channel region is formed using a semiconductor film which is formed over a substrate having an insulating surface is known. Techniques in which amorphous silicon, microcrystalline silicon, or polycrystalline silicon is used for the semiconductor film where the channel region is formed in the thin film transistor have been disclosed. Further, a thin film transistor is disclosed which includes, between a gate insulating layer formed over a gate electrode and source and drain regions, a microcrystalline semiconductor layer and a pair of buffer layers formed over the microcrystalline semiconductor layer and formed of an amorphous semiconductor (see Patent Document 1). A typical application of such a thin film transistor is a liquid crystal television device, in which the thin film transistor has been used as a switching transistor in each pixel in a display screen.